Sounds like your trying to pump to much fuel into the engine. The bigger injectors and fuel rail are nice to have but if the engine can't use the fuel you'll sputter out (flood) the engine. Also have you had the computer remapped or programed? The computer may be wacked out not knowing what to do with the bigger injectors, fuel rail, and not having an O2 sensor. I would imagine it originally came with an o2 sensor which helps the computer determine fuel mixture; might be a good idea to reinstall it.